chore: allow fork pr deployment for test pages

[amanabiy]

Description

Enables dev page previews for forked pull requests by triggering the reusable deployment workflow after the build completes and deploying the generated dev-pages artifact.

Related: cloudscape-design/actions#122

Related links, issue #, if available: AWSUI-53554

How has this been tested?

Review checklist

The following items are to be evaluated by the author(s) and the reviewer(s).

Correctness

• Changes include appropriate documentation updates.
• Changes are backward-compatible if not indicated, see CONTRIBUTING.md.
• Changes do not include unsupported browser features, see CONTRIBUTING.md.
• Changes were manually tested for accessibility, see accessibility guidelines.

Security

• If the code handles URLs: all URLs are validated through the checkSafeUrl function.

Testing

• Changes are covered with new/existing unit tests?
• Changes are covered with new/existing integration tests?

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 87.79%. Comparing base (d4a2b1d) to head (5387fd8).
⚠️ Report is 1 commits behind head on main.

❌ Your project check has failed because the head coverage (87.79%) is below the target coverage (90.00%). You can increase the head coverage or adjust the target coverage.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #146      +/-   ##
==========================================
+ Coverage   87.75%   87.79%   +0.03%     
==========================================
  Files          25       25              
  Lines         343      344       +1     
  Branches       93       92       -1     
==========================================
+ Hits          301      302       +1     
  Misses         42       42              

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